Background technology
Storer and logical device are most important component in the semiconducter device, and dielectric materials belongs to core in these two kinds of devices; The dielectric material that it both can be used as dynamic RAM (DRAM) electric capacity also can be used as the gate medium of cmos fet pipe logical device with canned data.Along with the develop rapidly of unicircuit according to Moore's Law, the characteristic dimension of device has been contracted to 90 nanometers, among 65nm and 45nm technology being are are being researched and developed.But small-size effect makes complete processing be developed near the limit, therefore must be by adopting new material or proposing the factor that new device model solves existing restriction development.For the DRAM of super-high density, require numerical information is stored in the littler area, and then require to keep the value of its electric capacity under the situation that the area at electrical condenser reduces.When capacitor dielectric thickness was constant, the unique method that keeps same capacitance size and reduce capacity area was the specific inductivity that improves electric capacity institute filled media, promptly adopts the high dielectric constant material.And, generally adopt SiO for the gate medium of field-effect transistor
2Medium.But along with the nanometer of device size, in order to suppress short-channel effect and to guarantee that device has good device property, the gate dielectric layer of requirement is more and more thinner, has caused many quadratic effects this moment, as: the Direct Tunneling Effect of electronics; The grid electric field of gate dielectric layer sharply increases the leakage current that causes worsens original basic device property, even can't works better.For this reason, the field-effect transistor of smaller szie must adopt high dielectric constant material to substitute traditional SiO as gate medium
2, to guarantee increasing the physical thickness of medium layer under the constant condition of equivalent thickness, to reduce the strength of electric field that Direct Tunneling Effect and gate dielectric layer bear.Strontium-barium titanate (BST) film by choose reasonable Ba/Sr ratio, can make material be in paraelectric phase as a kind of high-quality high dielectric material under the room-temperature applications temperature, the fatigue phenomenon of having avoided the ferroelectric domain switching effect to cause; It also has relatively low dielectric loss, less leakage current, and high specific inductivity, this has just in time satisfied the requirement of semiconducter device of future generation to dielectric materials, BST has been considered to be used to develop semiconducter device of future generation, as the important medium material of super-high density DRAM and nano-scale cmos fet pipe, BST will be the first-selection of hafnium in ITRS prediction 65 nanometer technologies in 2007.Nanometer along with device feature size, the photolithographic exposure resolution requirement of IC technology is more and more higher, by adopting shorter wavelength and bigger numerical aperture exposure system can improve resolving power, but cause simultaneously the depth of focus difficult problem that shoals again, this just requires the high planarization of exposed, and the unique technical that realizes the planarization of the wafer surface overall situation at present is exactly chemically machinery polished (chemical mechanical polishing, CMP), especially for the IC technology of characteristic dimension less than 0.25 micron, CMP has become one of key process technology.In conjunction with BST in semiconducter device of future generation growth requirement and nano-scale IC manufacturing process to the high planarization requirement of wafer surface, the CMP of relevant BST research seems and becomes more and more important, becomes the bottleneck of semiconductor device development of future generation.Consult domestic and international patent and document, the report of relevant bst thin film CMP is less up to now, and US5695384 discloses the salt polishing fluid of a kind of BST of being used for workpiece CMP, contains the water of 85wt% in the polishing fluid that this patent of invention provides, the NaCl of 4wt%, the H of 4wt%
2O
2And the colloid silica of 7wt%, the about 35nm/min of polishing speed.Owing to contain a large amount of Na in the polishing fluid
+, this is very harmful for semiconductor device technology, and polishing speed is low is difficult to satisfy industrial requirement.Yong-Jin Seo etc. has reported the CMP of the bst thin film of relevant employing sol-gel technology preparing, and the author has studied TiO in article
2As the polishing fluid performance of abrasive material, polishing speed can reach 320nm/min, but surfaceness is up to 1.50nm (Chemical mechanical polishing of Ba
0.6Sr
0.4TiO
3Film prepared by sol-gel method, Microelectronic Engineering 75 (2004) 149-154).For the requirements at the higher level of the growth requirement and the device of future generation of present device, the wafer surface roughness requires less than 1.0nm, even littler.CMP at the hafnium BST of super-high density DRAM and nano-scale cmos fet pipe, still need a kind of nanometer burnishing liquid, realize the glazed surface of high-level efficiency (polishing speed satisfies industrial requirement), high smooth (surfaceness is less than 1.0nm), low defective.
Summary of the invention
Based on the fast development of present semiconducter device (DRAM and nano-scale cmos fet pipe) and constantly dwindling of characteristic dimension, and to high dielectric material have an even surface require more and more higher, the present invention is directed to semiconducter device of future generation (DRAM and nano-scale cmos fet pipe) critical material---the dielectric material BST of high K (specific inductivity) carries out CMP research, the nanometer burnishing liquid of BST-CMP is provided and has utilized this polishing fluid that BST is carried out chemically machinery polished, for the development of high-performance of future generation, high-density, high reliability semiconductor device provides safeguard.
For DRAM, want to realize ultrahigh density storage, must adopt high K dielectric material and littler characteristic dimension technology; And for transistor, nanometer along with characteristic dimension, in order to suppress short-channel effect and to guarantee that device has good device property, gate dielectric layer is more and more thinner, many quadratic effects have been caused, sharply increase the leakage current that causes as: the grid electric field of the Direct Tunneling Effect of electronics, gate dielectric layer original basic device property worsened, for this reason the field-effect transistor of smaller szie must adopt high dielectric constant material as gate medium to substitute traditional SiO
2Thereby can guarantee increases the physical thickness of medium layer under the constant condition of equivalent thickness, to reduce the strength of electric field that Direct Tunneling Effect and gate dielectric layer bear.Along with feature sizes of semiconductor devices of future generation is more and more littler, photoetching resolution requires more and more higher, and high-resolution improvement has caused the problem that depth of focus shoals, and makes the Flatness of material surface is had higher requirement.Hafnium BST is a dielectric material important in the semiconducter device of future generation, the importance classes of its planarization research is similar to the CMP of Cu interconnection in the Deep Submicron IC technology.But up to now, very few about the CMP research of hafnium BST, the invention provides the nanometer burnishing liquid of hafnium BST-CMP, and utilize this polishing fluid hafnium bst thin film CMP.
Contain nano-abrasive, oxygenant, sequestrant, tensio-active agent, polishing promotor, defoamer, sterilant, pH regulator agent and solvent in the chemically machinery polished nanometer burnishing liquid that the present invention relates to.
Comprise at least a oxygenant in the CMP nanometer burnishing liquid provided by the invention.Oxygenant helps thin-film material is oxidizing to corresponding oxide compound, oxyhydroxide or ion.Form the compound or the reducible high valence ion compound of valence state of hydroxyl during the optional autoreduction of described oxygenant, as any one or two kinds in hydrogen peroxide, Urea Peroxide, the ammonium persulphate.Wherein excellent Urea Peroxide, ammonium persulphate or its mixture are as oxygenant.
Oxygenate content can be 0.5wt% to 15.0wt% in the nanometer burnishing liquid provided by the invention; Preferred oxidant content is 0.5wt% to 10.0wt%; Best oxygenate content is 1.0wt% to 7.0wt%.If adopt the Urea Peroxide oxygenant, urea and hydrogen peroxide molar ratio range are 0.50: 1~2: 1.If contain the 33.5wt% hydrogen peroxide in the Urea Peroxide, the 66.5wt% urea, then the optimum content of Urea Peroxide should be 3.0wt% to 21.0wt% mutually.
Comprise at least a sequestrant in the CMP nanometer burnishing liquid provided by the invention.The effect of sequestrant be with the metal ion of glazed surface and polishing fluid in a spot of metal ion form inner complex, the volume that helps to reduce the pollution of glazed surface metal ion and increase the polishing product makes the polishing back clean easily and removes.Described sequestrant can be selected from the sequestrant of non-metallic ion, as any one or wherein any two kinds of mixtures in ethylenediamine tetraacetic acid (EDTA) ammonium, ammonium citrate, the hydroxyethylethylene diamine tetraacethyl ammonium.A kind of or its mixture in optimization citric acid ammonium, the hydroxyethylethylene diamine tetraacethyl ammonium.
The content of sequestrant can be 0.1wt% to 10.0wt% in the described nanometer burnishing liquid; The content of preferred sequestrant is 0.1wt% to 5.0wt%; Best sequestrant content is 0.3wt% to 3.0wt%.
Comprise at least a metal oxide nano abrasive in the CMP nanometer burnishing liquid provided by the invention.Abrasive mainly acts on the mechanical friction when being CMP, optional self-alumina, titanium oxide, colloidal silica and composition thereof.The preferred titanium oxide of described abrasive, colloid silica and composition thereof.
Be used for abrasive median size of the present invention less than 200 nanometers, best median size is 10~120 nanometers.Described abrasive is the water dispersion of metal oxide or the colloidal solution of metal oxide.
Abrasive content can be 1.0wt% to 30.0wt% in the described CMP nanometer burnishing liquid; The content of preferred abrasive is 1.0wt% to 20.0wt%; Best abrasive content is 2.0wt% to 15.0wt%.
Comprise at least a tensio-active agent in the CMP nanometer burnishing liquid provided by the invention.The effect of tensio-active agent mainly comprises makes abrasive dispersive high stability in the polishing fluid; Be preferentially adsorbed on the surface of material surface in the CMP process, the chemical corrosion effect reduces, because that recess is subjected to frictional force is little, thereby protruding place is bigger than recess polishing speed, has played and has improved polishing convex-concave selectivity; Surface contaminant after tensio-active agent also helps to polish cleans.Be used for tensio-active agent of the present invention and can be nonionogenic tenside, cats product, anion surfactant; Can be selected from any one or two kinds of alkyl alcohol polyoxyethylene groups ether, alkyl trimethyl ammonium bromide, ammonium polyacrylate, the ammonium polymethacrylate of non-metallic ion; Preferred alkyl alcohol polyoxyethylene groups ether, ammonium polyacrylate, ammonium polymethacrylate and composition thereof.
Surfactant content is 0.01wt% to 2.0wt% in the described CMP nanometer burnishing liquid; Preferred surfactant content is 0.01wt% to 1.0wt%; Optimum surfactant content is 0.01wt% to 0.5wt%.
Comprise at least a polishing promotor in the CMP nanometer burnishing liquid provided by the invention.Consider that the product after the after chemical reaction of bst thin film material removes, the processing by oxygenant has formed BaO, SrO, TiO
2Etc. corresponding oxide, under the basic solution effect, form corresponding oxyhydroxide, but these several hydroxide all are the micro-soluble materials in the water, even insolubles, be deposited on glazed surface easily and form the particle pickup and influence further material removal.The present invention adds a kind of halogenide of not metal ion as promotor, forms water-soluble halogenide with above-mentioned oxyhydroxide, has strengthened the removal effect of surface film, has accelerated polishing speed; Suppress the formation of surface particles, reduced scuffing and roughness.Be used for the halogenide that polishing of the present invention promotor is selected from non-metallic ion, as Neutral ammonium fluoride, ammonium chloride and brometo de amonio any one or two kinds; Excellent Neutral ammonium fluoride, ammonium chloride and composition thereof.
The polishing accelerator content is 0.5wt% to 5.0wt% in the described CMP nanometer burnishing liquid; Preferred surfactant content is 0.5wt% to 4.0wt%; Optimum surfactant content is 0.8wt% to 2.0wt%.
Comprise a kind of defoamer in the CMP nanometer burnishing liquid provided by the invention, the adding of tensio-active agent causes foamy to produce usually in the polishing fluid, is unfavorable for explained hereafter control, realizes low bubble or still polishing fluid by adding the minute quantity defoamer, is convenient to manipulate.Defoamer of the present invention is selected from polysilane compound, as polydimethyl silane.
Antifoam content can be 20 to 200ppm in the described CMP nanometer burnishing liquid; Preferred antifoam content is 40 to 150ppm; Best antifoam content is 40 to 120ppm.
Comprise a kind of sterilant in the CMP nanometer burnishing liquid provided by the invention, contain many organism in the polishing fluid, long-term storage forms mould easily, causes polishing fluid rotten, adds a small amount of sterilant to reach this purpose in polishing fluid for this reason.Sterilant of the present invention is selected from thiazoles quinoline ketone compound, as the isomery thiazolinone.
Sterilant content can be 10 to 50ppm in the described CMP nanometer burnishing liquid; Preferred antifoam content is 10 to 30ppm; Best antifoam content is 10 to 20ppm.
Comprise at least a pH regulator agent in the CMP nanometer burnishing liquid provided by the invention.The pH regulator agent mainly is the pH value of regulating polishing fluid, makes polishing fluid stable, helps the carrying out of CMP.Be used for any one or two kinds of mixtures that pH regulator agent of the present invention can be selected from ammoniacal liquor, potassium hydroxide, Tetramethylammonium hydroxide, oxyamine; Preferred non-metallic ion compound is as ammoniacal liquor, Tetramethylammonium hydroxide, oxyamine and any two kinds of mixtures thereof.
Described nanometer burnishing liquid pH value is 7~12, and preferred pH is 8~11.5, and optimal ph is 8.5~11.
Solvent is a deionized water in the nanometer burnishing liquid provided by the invention.
Nanometer burnishing liquid provided by the invention can be used for high dielectric constant material CMP, and in particular for the dielectric material of the high-k of preparation super-high density DRAM and nano-scale cmos fet pipe, described high dielectric constant material strontium-barium titanate general formula is Ba
xSr
1-xTiO
3, 0<x<1.0 wherein.
Nanometer burnishing liquid provided by the invention carries out chemically machinery polished to the high dielectric constant material strontium-barium titanate and can be applicable to: the medium layer bst thin film (seeing embodiment 8 for details) that utilizes magnetron sputtering or sol-gel masking technique deposition high-k on silicon substrate, its polishing speed reaches 200~300nm/min, suitable with the bibliographical information value, but the surface of polished roughness is reduced to below the 0.8nm, so be a kind of comparatively ideal chemical mechanical polishing liquid.
Above-described high K dielectric material BST is difficult to realize better etching at present IC etch technological condition, and relevant chemically machinery polished research is less, by adopting nanometer burnishing liquid provided by the invention, can realize the overall planarization of high K dielectric material bst thin film, the roughness RMS of surface of polished satisfies the high planarization requirement of preparation high-performance, small size semiconducter device less than 0.8nm.
Embodiment
Further illustrate substantive distinguishing features of the present invention and marked improvement by following examples.But the present invention only limits to embodiment absolutely not.
[embodiment 1]
The preparation of nanometer burnishing liquid: contain the silicon dioxide colloid 20wt% of 10~30 nanometers in the polishing fluid, Urea Peroxide 12.0wt%; Hydroxyethylethylene diamine tetraacethyl ammonium is at 0.3wt%; Dodecyl alcohol polyoxyethylene base ether 0.2wt%; Ammonium chloride 1.0wt%, polydimethyl silane 50ppm, isomery thiazolinone 10ppm, Tetramethylammonium hydroxide is the pH regulator agent, and the pH value is 10.8, and all the other are deionized water.
[embodiment 2]
The preparation of nanometer burnishing liquid: contain the silicon dioxide colloid 5wt% of 10~30 nanometers in the polishing fluid, the titanium dioxide 4wt% of 40 nanometers, Urea Peroxide 10.0wt%; Ammonium citrate 0.5wt%; Ammonium polyacrylate 0.3wt%, dodecyl alcohol polyoxyethylene base ether 0.1wt%; Ammonium chloride 1.5wt%, polydimethyl silane 50ppm, isomery thiazolinone 10ppm, azanol are the pH regulator agent, and the pH value is 9.8, and all the other are deionized water.
[embodiment 3~7]
Embodiment | Abrasive | Oxygenant | Sequestrant | Promotor | Tensio-active agent | The pH conditioning agent | Other |
3 | SiO
2,10-30nm,5wt%; TiO
2,120nm,2wt%
| Ammonium persulphate 3.0wt% | Ammonium citrate 2.0wt% | Ammonium chloride 1.2wt% | Ammonium polymethacrylate 0.2wt% | Ammoniacal liquor, azanol, pH9.2 | Deionized water |
4 | SiO
2,10-30nm,5wt%; Al
2O
3,80nm,2wt%
| H
2O
21.0wt %, Urea Peroxide 5.0wt%
| Hydroxyethylethylene diamine tetraacethyl ammonium 1.0wt% | Fluoride amine 0.8wt% | Dodecyl alcohol polyoxyethylene base ether 0.3wt % | Tetramethylammonium hydroxide pH9.8 | Deionized water |
5 | Al
2O
3,80nm,5wt%
| Ammonium persulphate 4.0wt% | Ammonium citrate 3.0wt% | Fluoride amine 1.1wt% | Dodecyl sodium sulfonate ammonium 0.5wt% | Ammoniacal liquor, azanol pH10.2 | Deionized water |
6 | SiO
2,10-30nm,5wt%; TiO
2,120nm,2wt%
| H
2O
22.0wt %, ammonium persulphate 1.0wt%
| Hydroxyethylethylene diamine tetraacethyl ammonium 0.5wt% | Ammonium chloride 2.0wt% | Ammonium polyacrylate 0.1wt %, dodecyl alcohol polyoxyethylene base ether 0.1wt% | Ammoniacal liquor, azanol pH10.2 | Deionized water |
7 | SiO
2,10-30nm,5wt%; Al
2O
3,80nm,2wt%
| Urea Peroxide, 7.0wt% | Hydroxyethylethylene diamine tetraacethyl ammonium 0.5wt% | Ammonium chloride 0.8wt% | Ammonium polymethacrylate 0.1wt%, dodecyl alcohol polyoxyethylene base ether 0.1wt% | Ammoniacal liquor, azanol pH10.2 | Deionized water |
Annotate: the preferred median size of abrasive is 10~120 nanometers; Defoamer is a polydimethyl silane, and add-on is 50ppm; Sterilant is the isomery thiazolinone, and add-on is 10ppm.
[embodiment 8]
CMP test: the CP-4 polishing machine that adopts U.S. CE TR company, polishing pad is IC 1000/SubaIV, polishing machine chassis rotating speed 100rpm, rubbing head rotating speed 97rpm, polishing fluid flow 200ml/min, pressure is 3psi, and the composition that polishing fluid adopts above-mentioned 1~7 embodiment to provide respectively, polishing pad sample are Si/BST.Glazed surface is measured roughness RMS by atomic force microscope (AFM), the results are shown in Table 2.By table as can be seen, nanometer burnishing liquid provided by the invention carries out BST-CMP, and polishing speed can reach 200~300nm/min, and the surface of polished roughness RMS dropped to below the 0.8nm, can satisfy the planarization requirement of high-performance semiconductor device.
Table 2 polishing test-results
Polishing fluid | The BST polishing speed (/min) | Roughness RMS (nm) |
Polishing fluid 1 | 2180 | 0.77 |
Polishing fluid 2 | 3240 | 0.65 |
Polishing fluid 3 | 2630 | 0.68 |
Polishing fluid 4 | 2810 | 0.80 |
Polishing fluid 5 | 3020 | 0.72 |
Polishing fluid 6 | 3640 | 0.61 |
Polishing fluid 7 | 2040 | 0.80 |